Microwave and radio frequency (RF) filters are common components of communication devices. Both transmitters and receivers use filters for rejection of signals in the unwanted frequency bands. A major application of such filters is in cellular personal communications services (PCS) phones. The most commonly used filter for cellular PCS applications is the coaxial ceramic type in which several coaxial ceramic resonators with very high relative dielectric constants are coupled to each other. These filters are often installed on top of circuit boards and substantially increase the height of the board thickness. As a result, such filters are one of the components that restrict the implementation of thin cell/PCS phone designs.
A resonant cavity is a device having an enclosed volume bounded by electrically conductive surfaces and in which oscillating electromagnetic fields are sustainable. For example, resonant cavities may be used as filters and have excellent power handling capability and low energy losses. Several resonant cavities may be coupled together to achieve sophisticated frequency selective behavior.
This “Discussion of the Background” section is provided for background information only. The statements in this “Discussion of the Background” are not an admission that the subject matter disclosed in this “Discussion of the Background” section constitutes prior art to the present disclosure, and no part of this “Discussion of the Background” section may be used as an admission that any part of this application, including this “Discussion of the Background” section, constitutes prior art to the present disclosure.